Field of the Invention
The present invention relates to a method for producing a component from a TiAl alloy, in which the component is shaped by forging, in particular by isothermal forging, and is subsequently subjected to a heat treatment. In addition, the present invention relates to a component produced thereby.
Discussion of Background Information
TiAl alloys, the main constituents of which are titanium and aluminum, are distinguished by the fact that they have a high strength, in particular high-temperature strength, combined with an adequate ductility owing to the formation of intermetallic phases, for example γ-TiAl, which have a high proportion of covalent bonding forces within the metallic bond. In addition, they have a low specific weight, and therefore the use of the titanium aluminides or of TiAl alloys is suitable for high-temperature applications, for example for turbomachines, in particular gas turbines or aero engines.
The property profile of the TiAl alloys can be optimized further by adding certain alloying constituents, for example niobium and molybdenum. Alloys of this type with a niobium and molybdenum content are also referred to as TNM alloys.
These alloys are used in aero engines, for example as guide vanes or rotor blades, and are given the appropriate component shape by forging. In particular, use can be made here of isothermal forging with subsequent heat treatment for setting the microstructure and the property profile. In this way, it is also possible to produce single-part blade-disk units, what are termed blisks (coinage for blade and disk).
However, differences in the chemical composition over the component can lead, during production, to a different phase composition within a component made of a TiAl material; this results in a non-uniform distribution of the property profile in the component, and therefore corresponding variations in the properties over the component mean that components of this type can no longer be used if they lie outside the predefined specification for the component. This leads to high reject rates.